Boston police took over, tracking down and arresting David Lydon, 28, of Chelsea, after he allegedly robbed the bank on Dorchester Avenue near Richmond Street, said Boston police Officer Rachel McGuire. Police received a call reporting the robbery, around 2:22 p.m., according to the Boston police website.

Paciulli, 65, said he began the chase as soon as he heard a teller yell that the bank had just been robbed. He was able to catch up with the suspect and they exchanged a few punches, but the man was ultimately too big for Paciulli to subdue.

“It was quite the scene,” Paciulli said. “I caught up to him and he hit me a few times, and then I hit him once, and we were just going round and round.”

Paciulli said the man then reached in his pocket and pulled out a stack of $1 bills. He threw the bills at him and then casually walked down Richmond Street. Paciulli said he followed the man as he turned onto Swan Court, a dead-end side street.

“I could see that he was going to try and jump the fence [at the end of Swan Court], but he was too big to get over it,” Paciulli said. “Then I lost sight of him.”

After officers arrived on the scene, they found Lydon inside a nearby residence with the help of a K-9 unit, McGuire said. Officers were able to recover the stolen money after Lydon’s arrest, she said.

Lydon was charged with unarmed robbery of a bank, breaking and entering during the daytime, assault and battery on an elderly citizen, and for an active outstanding warrant.